The present invention relates to an improved catheter, and more particularly to an improved catheter which provides an increased viable lifetime and also minimizes potential trauma to the patient and the possibility of accidental needle contact with the medical practitioner.
Catheters are used for introducing fluids into an anatomical passageway of a patient undergoing treatment. Typically, a catheter is inserted into the anatomical passageway, such as a blood vessel. The catheter is then connected to an administration line from which fluids are introduced into the patient""s vascular system through the catheter. Alternatively, catheters may be placed directly into tissue of a patient, such as a muscle or organ so that a fluid medication may be administered directly to a specific site asystemically as is well understood by those of skill in the art.
There are various methods of inserting a catheter into an anatomical passageway. These methods typically involve the use of a sharpened metal needle in conjunction with the catheter. In one such method the metal needle defines a lumen. The metal needle is inserted into the patient""s anatomical passageway. Once the needle is in place, the catheter is introduced through the lumen and into the passageway. This type of catheter system is known as a through-the-needle system. Once the catheter is inserted, the needle is removed. This requires the medical practitioner to pull the needle with its sharp edge out of the patient and guide it over or along the catheter until it is removed.
Another type of catheter system is the over-the-needle system. In such a system, a catheter is placed over a rigid needle. The needle and catheter are simultaneously inserted into the patient""s anatomical passageway. Thereafter, the needle is withdrawn from the interior of the catheter, leaving the catheter disposed within the patient.
A common problem associated with many over-the-needle catheters is that they tend to travel axially away from the tip of the needle and thus collapse during the insertion procedure. The patient""s skin and tissue tend to resist the introduction of a catheter and push the distal tip of the catheter body backward. The catheter body thus wrinkles in an accordion or bellows-like manner over the needle as the distal end of the catheter travels backward toward the proximal end thereof while the needle is urged through the skin and tissue. This tendency of the catheter to wrinkle results from urging the catheter into the patient by applying a force to a separate needle as opposed to the catheter. Currently, virtually all over-the-needle catheters are formed of a single thermoplastic material such as polyvinylchloride (PVC), Teflon(copyright) polyurethane or the like, which provides stiff columnar strength during insertion. The catheter also remains relatively stiff when disposed within an anatomical passageway. Such stiffness traumatizes the walls of the anatomical passageway and typically requires removal of the catheter from the passageway or vessel in two days or less.
An over-the-needle catheter is described in U.S. Pat. No. 5,533,988, issued on Jul. 9, 1996 to Dickerson et al. and entitled xe2x80x9cOver-The-Needle Catheterxe2x80x9d. The catheter includes a flexible body and a hardened tip at the distal end. The hardened tip forms an abutment at the distal end of the catheter. A rigid needle extends within the catheter during the insertion process. The rigid needle engages the abutment in an attempt to prevent the catheter body from collapsing during the insertion process. The hardened tip may comprise a metal, among other materials. Optionally, the tip may comprise a plastic material which softens upon contact with moisture or upon reaching a temperature approximately equal to the patient""s body temperature.
A significant disadvantage of both the prior art through-the-needle and over-the-needle systems is that a sharpened needle must be removed once the catheter has been inserted into the patient. Removal of the sharpened needle undesirably exposes both the patient and the medical practitioner to accidental contact with the needle, a continuing problem in view of the highly contagious and/or fatal nature of such diseases as AIDS and Hepatitis A. Removal of the sharpened needle with the catheter in place also presents the problem of damage to the catheter itself.
Certain modifications have been made to minimize the possibility of accidental contact of patients or medical practitioners with the needle. One such modification is described in U.S. Pat. No. 5,683,370, issued Nov. 4, 1997 to Luther et al. entitled xe2x80x9cHard Tip Over-The-Needle Catheter and Method of Manufacturing the Same.xe2x80x9d The catheter assembly includes an introducing needle which includes a cylindrical protective guard or sheath which is slidably advanced over the sharp tip of the needle after the catheter is inserted and the needle is removed from the patient.
However, current devices and methods still require some action by the medical practitioner to remove and dispose of a sharpened needle immediately after inserting the catheter. The timing of this procedure presents drawbacks. Often a catheter is inserted at a moment when time is of the essence. For example, the patient may require emergency medical treatment. The risks associated with the removal of such sharp objects therefore could be minimized by waiting until the patient""s treatment is concluded, a time which often involves less haste and less risk to adversely affect a patient""s health.
In addition to the above-described drawbacks associated with present catheters, catheters have also exhibited a limited useful lifetime or viability. For example, present intravenous catheters typically need to be removed approximately every forty-eight hours and then a new catheter is inserted into a different area of the passageway to leave the passageway wall intact. Thus, a catheter must be replaced numerous times in even a short hospital stay by a patient which increases the risks of accidental sticks and contamination. Additional drawbacks are present as well. The removal and reinsertion of catheters increases the trauma to the patient""s anatomical passageways, e.g. blood vessels. The frequent replacement of catheters during the course of a patient""s treatment also increases medical costs, in terms of both time and materials. Accordingly, a catheter would ideally remain in place until the patient""s need for treatment with a catheter is completed. Several factors, however, affect how long a catheter may remain viable.
The principal reason for the need to frequently remove and replace a catheter relates to the trauma it causes to the patient""s anatomical passageways such as blood vessels. The trauma may be caused by movement of the patient and/or the portion of the catheter assembly located outside the patient. For example, with regard to an intravenous catheter such external movement is translated to the portion of the catheter located within the patient""s vein and causes the catheter to press against the inside wall of the vein. Such pressure may lead to damage to the inner walls of the patient""s vein or even internal bleeding. The flexibility of a catheter affects the degree to which it presses against the inside of the vein. Although catheters are generally flexible, they have not heretofore been flexible enough to alleviate the problem associated with a catheter pressing against the inside of a patient""s anatomical passageway.
Another problem associated with catheters relates to undesirable clotting of blood sometimes associated with certain materials of construction. Depending upon the material of construction of the catheter, blood may form clots when it is drawn up into the catheter. One such material which sometimes causes blood to clot is Teflon(copyright). Although the flow of fluids is typically from the catheter into the patient, the flow sometimes reverses. For example, when an instrument is removed from the fluid communication line connected to the catheter, it may result in a small decrease in pressure within the catheter thereby causing fluid to back up into the catheter from the patient""s vascular system. When the fluid within the tip of the catheter includes blood it may sometimes clot within the Teflon(copyright) catheter. Once flow is returned to normal, the clotted blood may be introduced back into the patient""s vascular system. This can lead to various problems. Because the tip of the catheter remains in contact with the blood when the catheter is disposed within a blood vessel, the material of construction of the inner portion of the catheter tip often plays a significant role in the degree of undesirable clotting.
The needle tip used in connection with the insertion of catheters, whether it be over-the-needle or through-the-needle systems, is typically formed by an oblique angle cut at the end of a hollow tube or cannula. While a needle formed in such a manner is highly effective for insertion, it can sometimes pass entirely through an anatomical passageway such as a blood vessel or can damage the opposing wall of the passageway during the insertion process. The degree to which such deleterious effects can be avoided depends almost entirely on the skill of the medical practitioner performing the insertion. Moreover, when the needle tip is to remain within the passageway for an extended period during treatment, such conventional needle tips may increase the possibility of trauma to the inside surface of the passageway depending upon the particular application. Therefore, a new catheter with a safety inserter is needed by those skilled in the art to increase safety of patients and healthcare workers alike.
The present invention provides a catheter comprising a flexible tube with a sharpened needle tip permanently secured to a distal end of the catheter to facilitate insertion of the catheter into a patient""s anatomical passageway. The sharpened needle tip secured to the catheter remains within the patient""s blood vessel during treatment. As a result, the invention does not require that a separate sharpened needle be inserted with the catheter and then removed immediately after the catheter is properly positioned.
Another feature of this invention is that it provides a catheter with increased flexibility to minimize trauma to the interior of an anatomical passageway such as a blood vessel, which increases the time period during which the catheter remains viable within the patient, and also increases the length of catheter which can be maintained within the anatomical passageway. The flexibility of the tube allows the needle tip to be flow directed towards the center of the vessel thereby minimizing trauma to the vessel and increasing the time period during which the catheter remains viable.
An additional advantage of the preferred embodiment of this invention is that it provides a catheter tip formed of a material which minimizes the clotting of blood which may back up into the catheter.
The preferred embodiment uses a retaining material adjacent the distal end of the flexible tube and extending around a portion of the circumference of the sharpened needle tip to secure the needle tip to the distal end of the catheter. To provide further support to the needle, one or more cavities are advantageously formed in the outer surface of the needle, which are filled with the material of the flexible tube, the retaining material, or both. Additional securement is provided by the melting and mingling of the two plastic materials comprising the flexible tube and retaining material when the needle tip is affixed to the distal end of the catheter.
A further feature of the preferred catheter assembly apparatus and method is that insertion of the catheter into a blood vessel or the like does not require a separate sharpened inserter to be used with the catheter. The catheter assembly comprises a catheter and a safety inserter. The safety inserter may be removably engaged within the catheter. Preferably, the inserter comprises a base portion and a distal end portion. The proximal end of the safety inserter is sized to accommodate a hydrophilic filter plug and/or a luer tip of a syringe. The distal end portion is sized to fit within the sharpened needle tip. The base portion is sized to fit within the flexible tube and to abut an annular shoulder formed by the proximate edge of the needle tip. Preferably, this inserter has a blunt distal end since the sharpened needle tip secured to the distal end of a flexible tube enables insertion of the catheter into the patient""s anatomical passageway such as a blood vessel.
In accordance with a further aspect of the present invention, the safety inserter has a closed distal end and corresponds to the shape of the needle tip at the distal end of the catheter. Such a catheter is particularly useful as an epidural catheter or a catheter to access implanted ports wherein no flashback is required.
In accordance with a further aspect, the invention provides a needle tip and method of forming the same wherein the point of the needle tip is substantially aligned with a central axis of the lumen defined by the needle tip or cannula from which it was derived. The improved needle tip minimizes the risk of injury to walls of an anatomical passageway.
Further features and advantages of the present invention will become apparent to those of skill in the art in view of the detailed description of preferred embodiments which follow, when considered together with the attached claims.